Hepcidin is the peptide hormone responsible for regulating circulating iron concentrations. Overexpression of hepcidin results in severe iron deficiency and anemia, whereas hepcidin deficiency leads to iron overload. Not surprisingly, abnormalities in hepcidin production and circulating concentrations are highly correlated with various disease states such as renal disease, cancer, hereditary hemochromatosis (HH), hypoxia, anemia of inflammation, infection, inflammatory diseases, and heart disease. Accurate methods for detecting hepcidin in serum will lead to improvements in our understanding, diagnosis, and clinical management of iron metabolism disorders. Unfortunately, there is no FDA approved assay for measuring hepcidin levels in serum. The development of a clinically relevant hepcidin assay has been hindered by hepcidin's very low immunogenicity, making it extremely challenging to produce antibodies against the hormone. The few immunoassays that do exist are poorly characterized in terms of specificity, and they struggle to differentiate hepcidin from the multiple inactive forms of the hormone that are found in the circulation. Affinergy will overcome these problems by using phage display biopanning to identify highly specific hepcidin-binding peptides. A peptide-based assay will circumvent the many challenges and limitations associated with the more traditional immunoassay approach, allowing us to accelerate the development of a clinically relevant hepcidin assay that will address a significant unmet need with the potential for widespread adoption.